When ethane, ethyl chloride, ethylene, 1,1-dichloroethane or a mixture of these compounds is reacted with chlorine at elevated temperatures there is produced 1,1,1-trichloroethane and vinylidene chloride, very desirable products. Also formed, however, are numerous by-products. It is common practice to conduct all or part of the high temperature chlorination reactor effluent to a liquid phase hydrochlorination reactor employing ferric chloride as catalyst, where unsaturated C.sub.2 by-products are combined with hydrogen chloride (also a by-product of the direct chlorination) to form saturated chlorinated hydrocarbons that can be recycled to the high temperature chlorination reactor to yield more of the desired products. For example, vinyl chloride is converted to 1,1-dichloroethane and ethylene to ethyl chloride in the hydrochlorinator. If increased yield of 1,1,1-trichloroethane is desired, vinylidene chloride can be passed through the hydrochlorination reactor where it is also combined with HCl to form 1,1,1-trichloroethane. Conversely, if vinylidene chloride is the desired product of the process, dehydrochlorination of 1,1,1-trichloroethane can be readily accomplished in an iron catalyzed, liquid phase reaction.
The major detrimental by-products of the high temperature chlorination with respect to further processing of the chlorinator effluent are unsaturated, chlorinated compounds containing more than two carbon atoms and although formed in relatively small quantities by various polymerization reactions which occur at these conditions, these products create problems. The ferric iron catalyst used in the hydrochlorination and/or dehydrochlorination steps of the process interacts with and is deactivated by small amounts of chlorinated, unsaturated by-products containing more than two carbon atoms such as those appearing in the reactor effluent. Thus, if these compounds are allowed to remain in the reactor effluent the efficiencies of the catalyzed hydrochlorination and dehydrochlorination steps of subsequent processing are greatly reduced. Because of their boiling points and concentration ranges relative to the various C.sub.2 's present in the effluent from a high temperature chlorination reactor, removal of the unsaturated polymerization products by distillation is very difficult. Also, removal of these compounds by any technique, e.g., distillation which involves their concentration is further complicated by their instability. Some of these compounds polymerize rapidly when concentrated, to form rubber-like polymers which plug process equipment.
It is well known that under the proper reaction conditions unsaturated hydrocarbons and chlorohydrocarbons can be readily and selectively reacted with elemental chlorine in the presence of much greater relative concentrations of saturated chlorinated hydrocarbons. However, the thermal chlorination reactor effluent even after quenching and flashing to remove the lower boiling compounds still contains valuable unsaturated C.sub.2 's in many times the concentration of the undesirable by-products which are to be chlorinated. Also, upon reaction with chlorine the unsaturated C.sub.2 's form compounds of little or no commercial value, e.g., vinylidene chloride chlorinates to yield tetrachloroethanes.
Therefore, it would be advantageous to provide a process for the deactivation of these unsaturated, chlorinated by-products containing more than 2 carbon atom compounds in the effluent of a thermal chlorinator before further processing the effluent stream.
This object as well as others will become apparent to those skilled in the art to which the invention pertains from the following description and claims.